The present invention relates to a compensating store device to be used in systems for directly feeding cigarettes from cigarette manufacturing machines to the hopper of a cigarette packeting machine.
As known, the plants in use at present for producing cigarettes comprise two different types of machine, i.e.:
1. Machines for producing cigarettes from cut and cured tobacco leaves, usually called cigarette manufacturing machines, and
2. Cigarette packaging machines.
The machines of the second type usually comprise:
Machines for producing packets of cigarettes, usually called packeting machines;
Machines for producing packs of cigarette packets, usually called packing or pack-forming machines, and
Wrapping machines for wrapping either single packets of cigarettes, called cellophaning machines, or single packs of cigarette packets, usually called "over wrapping machines".
In said plants, the cellophaning machines are located between the packeting machines and the packing or pack-forming machines, while the "over wrapping machines" are located downstream of or after the packing or pack-forming machines.
It is also known that there exist in practice various types of cigarette manufacturing machine operating at a respective output speed of 2000 to 4000 cigarettes per minute.
There also exist various types of manufacturing machines operating at output speeds ranging from 100-120 up to 400 packets of cigarettes/minute, whereas the output speed of the packing or pack-forming machines is a function of the number of packets forming the single packs. Among the wrapping machines for wrapping single cigarette packets, the type of cellophaning machine of the applicant's assignees which can wrap 400 packets of cigarettes per minute, is widely used. To wrap single packs, "over wrapping machines" operating at the same output speed as that of the packeting or packing machines co-operating therewith, are usually employed.
When considering the output speeds of the various types of machines in use at present, it is found that depending on the types of machine used in forming the plant, a packeting machine can absorb the output of one to three manufacturing machines, whereas a cellophaning machine can absorb the output or production of one to three packeting machines. As known, the cigarette supply from the manufacturing machine or machines to the packeting machine may occur substantially in two different ways, i.e.:
a. either by unloading the cigarettes into containers at the outlet of the cigarette manufacturing machine or machines, the containers being then transferred and unloaded into the assembling or grouping hopper arranged to feed the packeting line of the packeting machine, or
b. by directly connecting such outlet of the cigarette manufacturing machine or machines to the grouping hopper arranged to feed the packeting line of the packeting machine.
The present invention concerns the latter branch of the art, in which the outlet of the manufacturing machine or machines is directly connected to the grouping hopper of the packeting machine.
For such type of feeding system, it was already suggested to convey the cigarettes in a continuous or uniform flow from the manufacturing machine or machines to the packeting machine, the cigarettes, while being fed, being arranged in a succession of single cigarettes or batches of cigarettes by providing along the cigarette path means arranged to permit variations in the feeding flow as a function of the variations in the delivery capacity of the manufacturing machine or machines and of the receiving capacity of the packeting machine, respectively, so as to compensate for the frequently occurring unbalances in the output of said machines.
According to the proposals known at the present, said means arranged to permit volume variations in the cigarette flow as a function of the variations of the delivery capacity and the receiving capacity of said machines are provided, conceived and designed as having structures enabling them to act on batches of cigarettes, in contact with each other inside or outside the grouping hopper of the packeting machine.
On such batchwise treating of the cigarettes, piled up during both the simple transfer stages and particularly the piling up stages in order to compensate for frequently occurring unbalances in the output of the operating machines, the cigarettes are subjected to stress. This inevitably results, already in this initial stage of the process, in a damage to the cigarette features, in particular to the structural characteristics thereof (loss of compactness in the tobacco inside the cigarette envelope or paper).
For such reasons systems have been proposed for the direct feeding system mentioned in paragraph (b) above, in which various transfer means and even means arranged to permit changes in the flow rate act on single cigarettes rather than on cigarette batches. In order to eliminate the drawbacks due to direct connection between machines running at different operating speeds, such systems have used a compensating store device for compensating for unbalances which may occur owing to such different operating speeds, the cigarettes being stored one by one in the store and being withdrawn therefrom still one by one in case of need.
For instance, a device having a substantially cylindrical body which is about equal in height to the length of a cigarette and comprising radial compartments all around it, the compartments being about equal in width to the diameter of a cigarette and variable in depth, and being arranged to contain piles of cigarettes extending parallel to the axis of said cylindrical body, is already known. Such a device is continuously rotated about its own axis and its compartments, the depth of which uniformly increases or decreases depending on whether a storing or withdrawal operation is being performed, successively reach a well determined position where during each 360.degree. rotation every compartment receives a cigarette in the first operating condition thereof and delivers it in the second condition.
It should be noted that in view of this, such storing and withdrawing operations are carried out by following a spiral-like course.
From the above, it should appear that the maximum amount of cigarettes which can be stored is proportional to the diameter of the cylindrical body and this means that precise limits exist for the capacity and thus for the utility of such device.
Such compensating store is in fact subject to both size and weight limitations, the weight limitations being due to the fact that the speed of rotation of a particular storing and withdrawing mechanism has necessarily to match with the high output speed of the machines co-operating therewith.
It should also be noted that the cigarettes located in the innermost turns of said spiral will be only seldom withdrawn and this might be deleterious to the structural characteristics thereof.